Kinetic and structural data have revealed that chymotrypsin possesses an active site which is highly ionic in nature. The main reason for undertaking this research project is to investigate the electrostatic properties of the site for each stage of catalysis. This will be accomplished by studying both the ionic strength and dielectric effects on chymotrypsin-catalyzed hydrolyses. Since the ionic form of the site is pH dependent, the work will be done over a wide pH range using a variety of substrates, i.e., esters and amides, both specific and nonspecific. Chemically modified chymotrypsins will also be employed. This will add an important dimension to the study, in that, it should indicate which ionic groups are catalytic or binding and which are required for the conformation of the site.